Abstract:
The melon fly Bactrocera cucurbitae (Coquillett) is well known as a
destructive pest of fleshy fruits and vegetables in many parts of the world
including Bangladesh. Esterase (EST) isozyme banding patterns were
observed on 5% Polyacrylamide Gel Electrophoresis (PAGE) during the
different life stages (i.e. egg, larva, pupa and adult) and also sweet gourd,
which was used as larval food. Two bands, EST-1 and EST-2, showing
seven allelomorphs were found. There were four electromorphs in EST-1
(Est-104*’, Est-10'"’8, Est-10X7 and List-11 00), had a high mobility and close to
the anode and EST-2 had three allelomorphs (Est-2017, Est-20"7 and Est-
20'37), showed a low mobility and close to the cathode.
The standard photographic maps of salivary glands polytene
chromosomes were also observed in the different larval stages (lsl and 2"(l
instar larvae) of B. cucurbitae. In second instar larvae, the whole polytene
genome had been mapped by dividing it into 100 sections and the sub
sections were lettered. The banding pattern was moderately developed here.
The left end of the chromosome is characterized by dark bands in 4A. 6 and
14A. Sections 9 and 14B, each bears one pair faint bands. On the other
hand, 15 comprises one pair moderately dark bands. The expanded regions
in sections 3, 16 and 20 are not typical puff, rather section 16 bears a dotted
band. The tip (section 1) has faintly stained two bands. Weak points are
VIII
found in 2 and 19. Deeply stained bands occur in sections 30, 31 and 41.
Sections 33 and 40 are characterized by dotted bands; 39 and 42 comprise
two moderately developed pulTregions. Breakage occurs at 26. Sections 52,
55- 57 are characterized by a series of dark bands. Sections 48 and 50 have
similar single band. There is a poorly developed puff region in section 58.
Lightly stained two pairs of bands present in section 68. Sections 72, 73, 74
and 79 possess single band. One pair lightly stained bands occurs at 77 and
78. There is a prominent puff in section 80 together with a dark band
immediately proximal to it. Weak points arc found in 63, 76 and 81. Section
83 possesses three clear bands. A scries of lightly stained and deeply
stained bands are found in the sections 87 and 95. Section 100 appears only
as a well-developed puff in the total polytene chromosome complement.
Three weak points are found in 91, 97 and 98. In the case of Ist instar
larvae, salivary gland cells were at early stages of maturity. So the banding
pattern of polytene genome was not developed at this stage.
This observation showed that B. cucurbitae is an excellent genetical
material for esterase isozyme and polytene chromosome analysis. The
investigation has been proved to be very useful for obtaining more detailed
genetic information on the natural populations of this pest